cron FIFO in mounted spool filesystem

[Roger Knopf 5502]

In article <732 at wshb.csms.com> michaelb at wshb.csms.com ( WSHB Operations Eng) writes:
>I'm trying to move my /usr/spool directory to a seperate filesystem on a
>second hard disk in SCO XENIX 386 2.3.2. I didn't have any trouble
>making the filesystem or getting it to mount. I created all of the
>directories normally in /usr/spool, set it to automatically mount
>at boot, and changed cron startup to the user daemons (/etc/rc.d/7)
>so it would start after the filesystems were stable. I haven't tried
>to run the system this way because I noticed there is a FIFO in
>/usr/spool/cron that gets covered when I mount /dev/spool on /usr/spool.
>
>I had thought cron would create a new FIFO on startup and remove the old FIFO
>on shutdown. Obviously I'm wrong. What does this FIFO do? Can I cover
>it up with impunity, or will cron choke and puke because the FIFO is
>gone? Is there some way I can trick link to link it across the filesystem
>boundry? (What the hell is a FIFO anyway? This is one of those magic
>things about unix I've never understood.) 

First: a FIFO is a named pipe. Programs (such as crontab) can write to
it and other programs (such as cron) can read from it without knowing
directly about each other as you would to establish a regular pipe.

The FIFO is there for crontab to communicate with cron. You can make
it in your new filesystem by doing:

	# /etc/mknod FIFO p
	# chown root FIFO
	# chgrp bin FIFO
	# chmod 755 FIFO

or even easier, after you have mounted your spool file system:

	# cd /
	# /etc/fixperm -cs -dRTS /etc/perms/rts

-- 
Roger Knopf                                      <standard disclaimer applies>
SCO Consulting Services			  "The True Believers will...formulate
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